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Home My WebLink About9 High Pressure Methane for CoalHigh pressure methane adsorption analyses for coal samples of the Matanuska Valley coalbed methane AK 94CBM1hole as follows Seam No1 Seam No6 Seam No9 and Seam No 13 tw1159 I 42 Q 4A1Ta Jr Received 2 January 1998 Total of 24 pages in report Alaska Geologic Materials Center Data Report No 278 GMC Data Report 278 Page 1 of 24 High Pressure Methane Adsorption Analyses For Sarnples Seam 1 Canister 1 2 Seam 6 Canister 1114 Seam 9 Canister 20 Seam 13 anister 343537 For Dan Seamount UNOCAL PETROLEUM LTD Analyses carried out by RM Bustin 092197 GMC Data Report 278 Page 2 of 24 Results of Adsorption Analyses The adsorption analyses of the four provided samples are attached in both PSI andMFa units No difficulties were encountered in any of the analyses although equilibrium times were long which undoubtedly reflected the high equilibrium moisture content of the samples The dry ash free basis was determined utilizing the ash content we determined from the samples used in the analyses rather then the ash content provided by Unocal The enclosed DOS formatted 35 inch disk includes the reports for each sample for your convience The reports are in EXCEL v7 format Please refer to Appendix 1 for an overview of the analyses technique If you have ques1tions regarding your isotherms do not hesitate to contact me Table 1 SUlmmary of EQ moisture and Langmuir volumes of the analzed samples EQ ASII LAN IlJlE 1llY i VOL cCJ Seam 1 Canister 12 Seam 6 Canister 1114 Seam 9 Canister 20 Seam 13 Canister 343537 1066 842 771 948 1286 2326 1504 404 110 149 156 138 Saturated Monolayer Volume ft3ton @ STP daf 354 Correlation Coefficient 09843 Langmuir Pressure PSI 1039 Std error of Langmuir volume 1 2 315 384 436 476 523 556 591 618 649 420 812 1105 1310 1472 1643 1775 1880 1994 132 312 482 623 770 913 1049 1162 1295 I DATA CORRECTED FOR ASH AND MOISTURE CONTENT 412 502 571 622 683 726 773 809 849 321 621 845 1002 1126 1256 1358 1438 1525 132 312 482 623 770 913 1049 11 E2 1255 PVADSORBED METHANE ft3ton PRESSURE PSI Sample LD Seam 1 Cannister Moisture Content EO 1 2 1066 Isotherm Temperature 300 Ash Content dry basis 1286 Helium Density glee 1424 COAL lETHANEADSORPTION ISOTHERM Page 3 of 24GMCDataReport278 GMC Data Report 278 Page 4 of 24 COAL METHANE ADSORPTION ISOTHERM Sample ID Seam 1 Cannister Moisture Content EQ 1066 12 Isotherm Temperalture 30C Ash Content dry basis 1286 Helium Density glee 1424 PRESSURE MPa ADSORBED PV METHANE cclg 0913 100 0915 2152 193 1115 3324 262 1267 4296 311 1381 5306 350 1517 6293 390 1613 7232 422 1715 8015 446 1795 8927 474 1885 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 0913 2152 3324 4296 5306 6293 7232 8015 8927 130 252 343 407 457 510 551 584 619 0700 0853 0969 1056 1160 1234 1312 1373 1 441 Saturated Monolayelr Volume ccg @ STP daf Correlation Coefficient Langmuir Pressure MPa Std error of Langmuir volume 2 110 09843 71605 1400 1200 LL c c a 1000 rJ @ C u 800 C U c o en C c 600 U C 0 s J U E 400 200 000 o 2 Seam 1 Cannister 1 and 2 I 4 I 6 I 10 I 8 Sample Cell Equilibrium Pressure MPa a t Otj o N J I 12 JQ V o It N I 14 16 GMC Data Report 278 COAL METHANE ADSORPTION ISOTHERM Page 6 of 24 Sample ID Seam 6 Cann 11 Moisture Content EO 842 14 Isotherm Temperalture 30C Ash Content dry basis 2326 Helium Density gee 1503 PRESSURE MPa ADSORBED PV METHANE eeg 0876 108 0812 2044 204 1004 3242 276 1173 4240 335 1265 5211 381 1366 6179 422 1463 7127 466 1530 7858 494 1592 8576 524 1636 9216 562 1641 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 0876 2044 3242 4240 5211 6179 7127 7858 8576 9216 0555 0686 0801 0864 0933 1000 1045 1087 1118 1121 158 298 405 491 558 618 682 723 767 822 Saturated Monolayer Volume eclg @ STP daf Correlation Coefficient Langmuir Pressure Mpa Std error of Langmuir volume 2 149 09707 82415 GMC Data Report 278 Page 7 of 24 COAL METHANE ADSORPTION ISOTHERM Sample ID Seam 6 Cann 11 Moisture Content EO 14 842 Isotherm Temperature 30C Ash Content dry basis 2326 Helium Density glee 1503 PRESSURE PSI ADSORBED METHANE ft3ton PV 127 2919 470 615 753 8913 10314 1140 1244 1337 347 656 890 1079 1228 1360 1500 1590 1688 1808 366 452 528 570 615 659 689 717 737 739 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 12r 29E 470 6H 75E 89E 1034 1140 1244 1337 509 959 1303 1580 1798 1990 2196 2327 2470 2647 250 309 361 389 420 450 471 490 504 505 Saturated Monolayer Volume feton @ STP daf 479 Correlation Coefficient 09707 Langmuir Pressure PSI 1195 Std error of Langmuir volume 2 Sample Cell Equilibrium Pressure MPa IC Jq 1 00 o It N 400 200 000 I I I I I I I 0 2 4 6 8 10 12 14 16 a d p t p 10 1 d o N 00 Seam 6 Cannisters 1114 iL c c 1400 0 I UJ @ 1200 en u u 1000 4 c o 800 c CD c ns 5 600 CD 1600 18002000 GMC Data Report 278 COAL METHANE ADSORPTION ISOTHERM Page 9 of 24 Sample ID Seam 9 Cann 20 Moisture Content EO 771 22 Isotherm Temperalture 30C Ash Content dry basis 1504 Helium Density gee 1399 PRESSURE MPa ADSORBED PV METHANE ceg 0698 125 0556 1847 248 0745 3140 350 0897 3559 379 0938 4560 442 1031 5241 489 1072 6324 562 1 126 7240 619 1170 8084 674 1199 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 0698 1847 3140 3559 4560 5241 6324 7240 8084 162 321 453 491 572 633 727 801 873 0429 0576 0693 0725 0797 0828 0870 0904 0926 Saturated MonolayerVolume cclg @ STP daf Correlation Coefficient Langmuir Pressure MPa Std error of Langmuir volume 2 156 09341 71448 GMC Data Report 278 Page 10 of24 COAL METHANE ADSORPTION ISOTHERM Sample ID Seam 9 Cann 20 Moisture Content EQ 22 771 Isotherm Temperature 30C Ash Content dry basis 1504 Helium Density glee 1399 PRESSURE PSI ADSORBED METHANE ft3ton PV 101 2613 455 5113 661 760 917 1050 1172 404 798 1127 1222 1424 1575 1809 1993 2171 250 336 404 423 465 483 507 527 540 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 1011 26a 45S 511 661 760 91i 1050 1172 523 1033 1459 1582 1843 2038 2341 2580 2810 193 259 312 326 359 373 392 407 417 Saturated Monolayer Volume feton @ STP daf 501 Correlation Coefficient 09341 Langmuir Pressure PSI 1036 Std error of Langmuir volume 2 400 200 000 I I I I I I 0 2 4 6 8 10 12 14 16 2000 1800 1600 iL 1400 0 I U @ 1200 C U u 1000 Q c o 800 Q c tU 5 600 Q Seam 9 Cannisters 2022 a n d P P d o tv J 00 JQ 1 o I tv Sample Cell Equilibrium Pressure Mpa GMC Data Report 278 Page 12 of24 COAL METHANE ADSORPTION ISOTHERM Sample ID Seam 13 Cann Moisture Content EO 948 343537 Isotherm Temperature 30C Ash Content dry basis 404 Helium Density glee 1370 PRESSURE MPa ADSORBED PV METHANE ccg 0848 129 0657 2065 258 0799 3240 349 0929 4292 413 1040 5296 465 1140 6264 536 1168 7194 590 1219 8107 623 1302 8738 653 1338 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 0848 2065 3240 4292 5296 6264 7194 8107 8738 149 299 403 477 537 620 682 720 755 0568 0691 0803 0899 0986 1010 1054 1126 1157 Saturated Monolayer Volume ccg @ STP daf Correlation Coefficient Langmuir Pressure MPa Std error of Langmuir volume 1 2 138 09762 76185 GMC Data Report 278 Page 13 of24 COAL METHANE ADSORPTION ISOTHERM Sample LD Seam 13 Cann Moisture Content EO 948 343537 Isotherm Temperature 30C Ash Content dry basis 404 Helium Density glee 1370 PRESSURE PSI ADSORBED PV METHANE ft3ton 123 416 296 300 832 360 470 1123 418 622 1329 468 76a 1496 513 900 1727 526 1043 1900 549 1176 2006 586 1267 2104 603 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 12 300 47CI 622 76S 9061 1043 11713 1267 480 962 1299 1536 1730 1997 2197 2319 2432 256 311 362 405 444 455 475 507 521 Saturated Monolayer Volume ft3ton @ STP daf 445 Correlation Coefficient 09762 Langmuir Pressure PSI 1105 Std error of Langmuir volume 1 2 o N Sample Cell Equilibæum Pressure MPa 16 I 14 I 12 I 4 I 2 I 10 I 8 I 6 JQ D o s t1 OD U o N 00 Seam 13 Cannister 343537 o 000 500LLc 0t en @ 1500 C Ł3 C U c o 1000 U c co c U 2000 2500 ALASKALAND GAS CONSERVATION COJSSJON WELL OMPLETINOR RECOMPLErlON 111PORTADOQ t SUfi of WU ClwUIettfIof Sttvlc II OIL CJ GAO SUSHNCfO 0 ABANCONIrJi uvlce 0 I L N ttI Of OHlfOt oS Q 1IP r D 1 0 1 Acid a AP t NunlDlf Po tOo1 t4IttłAJ 1950 10 c IoaronDI WIll t tfau J D Unit OJ LdJA Nam A Top IQ11 F L 3 3 fSL Sc 3ITlBJQ W S iQw IcrY11 1 fi1Gand 001 ce FM Permit Nu Cb9 At To tpth S IIyarkllnfcjloiluKa DF tel 6 Luu OtloftIStl1 No 12 jjf u 31˛n 4Dator 1S Wa łt its 16 I 17 TottI CUMOrv PI PIIaack OlhIMoTVQI 1 01rotiOMI rvtv 20 Oeprh rusv t nllek1of Ptan J fS f rSC NO Z tur MO 0 n Tv flactrlt Ot Othtr 0wn cclj Tp s p 2 C´INC SIZE WT PER Y CAOe 6Pt 5 ttS Pc S I R e n pCt I1 1Ne vn J CASINOL INe ANO CEMENTING CORO SIiTIINGC PTt1 MO TOP BOTTOM u J G f y HOLESI ICMENTING ReCORe l 3 oS tAMOUNTVLIIO r tPrlOrl1tontopln te PraclwGtlonMD tTVC of To IndOHon l nd1n1lMI sin urwm rl NONe 26 SIZfl ł 8ACID ItACTU˜ECMeN T SQUEII ETC OEPTH INTSRVAI IMOI AMOUNT KINO OFMorER1AL 10 r TUSlINQ eCORC Ii DEPTH SIT MO PACKER SET MOl 27 Oar Flm PrOGwCtlon ROOUCtlON TEn IMthOd ofO rnJlIW1f1mllh ttOCt 0 1MOcltlT utGfROOUCTIONFOROI1 aSI Iaß MCFWATA ISISI CHOKE SIZQAS OIL ATIO TESTpaH IOO IowTubil OCNinltluurCALQUU TED01 881GASM F IWATER8UOILCiRAvITYI 1f grrlPr au2fOUR RA TI 21 CO OA1A8rl tdHCTiptlonf IhhalOno rhacturts lłłareru dlMdttafttl of clI 01lrJ mlt cor Chip C uOt C e ˙f3 64 TO11of STo Ac o cAb H J 0 Go IV Ct ec1Ltt 1cs10 CI n 60CONTlNUEO ONAfVIP U 10Ih Indui 1tGMCDa eport 278 Page15of24 GMC Data Report 278 AK 94CBMl t lASBUILT OF CONDUCTOR I N LOCATED WITHIN SE14 SE14 Sec 3 T 8 N A WSeWARDMERIDIAN AIK Latitude e 1 3et2N Long Itude 14931 02 W NAC 1927 Y 2776281X584064ZONE4 Top of Conductor 7894 406 MEP Page 16 of24 31 32 200 050 KZ 100 14 COR Recovered Bent IPNoCap Q z a T 1e to T 7 N VICINITY MAP SILVER LEAF ESTATES SW´hD MiCA NUMBER SCAEifK94rRMlr 301 x SO VISQUE ENLINED J 11SnRESERVEPITrTOBEREMOVED lNG 5 WATE WELL I MI i PRIVATE LAND DONALD CHURCHOWNERI7894 I Reooverdbent iron pipe100r132Ittbrallcap tt l 4l OSO T 1 S N T 17 N 200 6 5 o Found 31 Aluminum monument no marks Found 5S rebar with Aluminum cep marked DB 100 R P 14 Cor 4118577 typical I HEREBY CERTIFY THAT AM PROPERLY RISTEFEDAND LICENSEO TO PRACTICE LAND SURVEYING IN THE STATE OF ALASKA THATTHI ASBUILT REPRESENTS A SLJRVEY MADe BY ME OR UNOE MY OIRECT SUPERVISION THAT THE MCNUMeNTS SHOWN HEREON ACTUALLY EXIST AS DESCRIBED AND THAT AI L DIMENSIONS AND OTHER DETAILSARE CORRECT I r `CATE 7 9 R EGISTATION NO eBBS 1 Pr1EPARED BY DATE OF PREPAREO FOR LEGAL DESCRIPTION JRVYi 3teo of k ac SCcgc 21 Depar1ment of Na1ural ROlourcle 1 TOWSHI aN Juy 81ie4 I DiviinofOii andGas RANE w O Œ3o 07034 l AIhcrgAK ees O10 SHEET 1 GMC Data Report 278 Well AK94CBM1 COAL METHANE ADSORPTION ISOTHERM Sec 31 T18NR1W Sample ID Seam 1 Cannister 1 2 Isotherm Temperature 30C Depth 522 to 524 Gas Yield 63 sefton PRESSURE PSI Moisture Content EQ Ash Content dry basis Helium Density glee ADSORBED METHANE ft3ton 1324028729 3120592965 4821754564 6230181866 7695389164 9127438045 1048858256 1162494647 1294723873 3212770473 6210643714 8450242913 1001707536 1125997857 1256378853 1357711957 1437589019 1525172002 Page 17 of24 1066 1286 1424064 PI V 4121143 5024589 5706054 6219562 6834284 7264877 772519 8086419 8489035 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 1324028729 3120592965 4821754564 6230181866 7695389164 9127438045 1048858256 1162494647 1294723873 4200798213 812061155 1104895778 1309764038 1472277533 1642754776 177525099 1879692755 1994210253 Saturated Monolayer Volume ft3ton @ STP daf COlrelation Coefficient Langmuir Pressure PSI Std error of Langmuir volume 1 2 315185 3842805 436399 4756721 522686 5556178 5908225 6184493 6492414 3536433 0984256 1038548 GMC Data Report 278 Well AK94CBM1 COAl METHANE ADSORPTION ISOTHERM See 31 T18NR1W Sample ID Seam 6 Cann 1114 IsothermTemperature 30gC Depth 893 to 897 Ga Yield 177 sefton PRESSURE PSI Moisture Content EO Ash Content dry basis Helium Density glee ADSORBED METHANE ft3ton 1270870967 2964365408 4702341406 6148963432 7557365649 8962449136 1033662084 1139675904 1243778986 1336683134 3474673771 6555224685 8902788105 1079321596 1228141193 1359606702 1500053803 1589678649 1687611434 1808281534 Page 18 of24 842 2326 1 503062 PIV 3657526 4522142 5281875 5697063 6153499 6591942 6890833 7169222 7370055 7392008 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 1270870967 2964365408 4702341406 6148963432 7557365649 8962449136 1033662084 1139675904 1243778986 1336683134 5085880813 9594883906 1303101303 1579803273 1797630552 1990056647 21956291o 2326813011 2470157251 2646782104 Saturated Monolayer Volume ft3ton @ STP daf COIrelation Coefficient Langmuir Pressure PSI Std error of Langmuir volume 1 2 2498822 3089527 3608577 3892234 4204071 4503615 4707817 4898012 5035222 505022 4525862 0989984 1129701 GMC Data Report 278 Well AK94CBM1 COAL METHANE ADSORPTION ISOTHERM Sec 31 T18NR1W Sample ID Isotherm Temperature PRESSURE PSI 101 19783915 26786080514 4553822906 5162608189 6613188627 7601130141 9172264845 1050060418 1172496525 101 197835 26786080S4 4553822906 51626081a9 661318867 7601130141 9172264845 10500604 18 1172496535 Seam 9 Cann 2022 30QC Depth 1064 to 1068 Gas Yield 163 sefton Moisture Content EO Ash Content dry basis Helium Density glee ADSORBED METHANE ft3ton 4040906229 7978816926 1127176817 1221886497 1423650711 157450101 1808776874 1992955444 2170996544 Page 19 of24 771 1504 1398678 PV 2504335 3357149 4040025 4225113 4645233 4827644 5070976 526886 540073 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 5230946574 103285656 1459128566 1581730093 1842913542 2038189009 2341458737 2579877598 2810351514 Saturated MonolayerVolume ft3ton @ STP daf Correlation Coefficient Langmuir Pressure PSI Std error of Langmuir volume 1 2 1934599 2593398 312092 32639 3588442 3729355 3917329 4070195 4172064 5010922 0934066 1036264 4449592 0976173 1104974 2559774 3111965 3617534 4051385 4439309 4549754 4748429 506987 5210499 531 245 1229881164 4804647717 2995163541 9624669032 4698892224 1298921223 6224803223 153646297 7681625492 1730365061 908526128 1996868505 1043419418 2197399224 1175890463 2319369914 1267383353 2432364697 3000 445 Saturated Monolayer Volume ft3ton @ STP daf Correlation Coefficient Langmuir Pressure PSI Std error of Langmuir volume 1 2 DATA CORRECTED FOR ASH AND MOISTURE CONTENT 2959961 359848 4183088 4684765 5133336 5261048 5490783 5862477 6025091 948 404 136991 Page 20 of 24 4155059346 8323413779 1123307074 1328733176 1496419705 1726891883 1900310849 2005791101 210350899 1229881164 2995163541 4698892224 6224803223 7681625492 908526128 1043419418 1175890463 1267383353 PVADSORBEDMETHANEft3tonPRESSUREPSI Moistu re Content EQ Ash Content dry basis Helium Density glee Seam 13 Cann 343537 302C Depth 1235 to 1240 Gas Yield 245 sefton Sample ID Isotherm Temperature Well AK94CBM1 COAL METHANE ADSORPTION ISOTHERM Sec 31 T18NR1W GMC Data Report 278 GMC Data Report 278 Page 21 of24 APPENDIX 1 Your Isotherms To help you interpret you data I have prepared a few short paragraphs to tell you how your data was obtained If you have any questions please do not hesitate to contact us Obtaining and interpreting isotherm data and Langmuir Isotherms Your highpressure methane carbon dioxide or mixed gas adsorption analyses were performed using a highpressure volumetric adsorption technique similar to that described by Mavor et al 1990 Your isotherms were measured on a custom made apparatus modeled after an apparatus designed and built at CSIRO Lucus Heights Australia The apparatus is based on Boyles Law Simply a known volume of gas within in a reference cell is used to dose a sample cell containing your sample The amount of gas adsorbed using the real gas law in the sample cell is then determined based on change in pressure in the sample cell Normally 100 g of sample is utilized in such analyses Tests show that reproducible results can be obtained on samples as small as 25 g but the larger samples yield bettler quality data Our instrument has four sample cells The pressures in the reference and four samples cells are measured using pressure transducers that alre interfaced to a computer equipped with specialized boards and software for this purpose The computer monitors the transducers and determines when equilibrium is reached as well as controls valves and switches for dosing and purging the references and sample cells Following dosing of the sample cell with a known volume of gas the pressure in the sample cell is monitored As gas is adsorbed by the sample the pressure drops until equilibrium is reached that is no more gas can be adsorbed by the samples at that particular specified pressure Critical to obtaining quality isotherms is deciding when the equilibrium is reached In our instrument we set a stringent test equilibrium is reached only when the pressure in the cell does not change over a designated period of time When equilibrium is reached the sample is dosed at the next highest pressure We normally collect 12 separate pressure points selected such that the best Langmuir regression can be obtained We can of course collect data at points selected by the client before hand The temperate of the references and sample cells is maintained at the exact temperate requested by the client The temperate is maintained within a tolerance less than 110 of one degree centigrade For a routine adsorption analyses about five to six days are required once equilibrium moisture has been determined GMC Data Report 278 Page 22 of 24 How we assure the quality of the isotherms potential sources of eor and recognition ofproblems With an apparatu such as ours the only potential error is a change in the characteristics of the pressure transducers a leak in the system or nonisothermal conditions Our pressure transducers were selected for optimum performance within the range of pressures that isotherms are collected They are not only factory guaranteed we cross calibrate our transducers periodically to test for drift The accuracy of our transducers is better than 0001 MPa Prior to running your experiment the reference and sample cells and plumbing are pressure tested for leaks using helium We do our leak tests at 7 MPa Because the He molecule is smaller than either methane or carbon dioxide the gases we normally do adsorption work with using He assures us of a leak free system If a leak were to develop during analyses one never has it would be readily apparent because the cells would never come to equilibrium at a given pressure the leak would appear as an infinitely adsorbing material Nonisothermal conditions are not a potential problem utilizing our instrument unless a prolonged power failure occurs Our bath temperature is maintained by a submerged electric heater and a circulating power The heater is controlled by a temperature controller to a tolrance less than 110 of a degree centigrade We periodically nm a standard sample in our apparatus to confirm that all is well Understanding our Isotherms The classic theory used to describe the Type I isotherm for microporous materials with small external surface area is based on the Langmuir equation 1916 The Type I isotherm displays a steep increase in adsorption at low relative pressures due to enhanced adsorption caused by the overlapping adsorption potentials between walls of pores whose diameters are cOITlmensurate in size with the adsorbate molecule The Type I isotherm then flattens out into a plateau region at higher relative pressure which is believed to be due to the completion of a monolayer of adsorbed gas The micropore volume is then thought to be filled by only a few molecular layers of adsorbate and further uptake is limited by the dimensions of the micropores The Langrnuir model assumes that a state of dynamic equilibrium is establishd between the adsorbate vapor and the adsorbent surface and that adsorption is restricted to a single monolayer Gregg and Sing 1982 The adsorbent surface is thought to be composed of a regular array of energetically homogeneous adsorption sites upon which an adsorbed monolayer is assumed to form The rate of condensation is assumed to be equal to the rate of evaporation from the adsorbed monolayer at a given relative pressure and GMC Data Report 278 Page 23 of 24 constant temperature The Langmuir equation was developed with these assumptions and takes the following form E L V BVm Vm where P is the equilibrium pressure V is the volume of gas adsorbed at equilibrium V m is the volume of adlsorbate occupying a monolayer and B is an empirical constant A plot ofPN Vs relative pressure should yield a straight line whose slope will yield Vm from which the surface area may be obtained As shown on your figures a best fit Langmuir isotherm and the data points have been plotted for each sample The Langmuir Isotherm can be written VP p P gas pressure VP predicated amount of gas adsorbed at P VL Langmuir volume parameter PL Langmuir pressure parameter The difference between the measured amount of gas adsorbed VP and that predicted using the Langmuilr Equation ViP is a measure of error and is given as ErrP ViP yep This error may be positive or negative The square of the error is always positive and is a measure of the how well the calculated isotherm matches the data This error can be calculate for each point and summed giving a measure of the overall error N 2 SSE LEr 1 I N number of measured points We express the goodness of fit of the isotherm by calculation the correlation coefficient between the measured points and the calculate points Our results generally yield correlations that are better than r2 099 and standard errors ofLanmuir volumes off 2 The errors fbr your samples can be found on the bottom of the data sheets that are included with each sample GMC Data Report 278 Page 24 of 24 In examining your data you should note that adsorption values are provided for the raw data and corrected for ash content The ash content will also be corrected for equilibrium moisture content When does adso1JJtion notfit a Langmuir Equation The Langmuir equation has been found to provide an excellent fit for almost all samples under most reservoir conditions The Langmuir equation is based on the assumption of monolayer filling of pores Under conditions of low temperature and very high pressures however multilayer pore filling takes place which results in a deflection step in the isotherm which marks the onset of multilayer pore filling This step occurs at pressures and temperatures that are not realistic in terms of natural reservoirs however since we routinely run our isotherms to pressures in excess of 1211Pa and many clients request low temperatures the step may be present in your isotherm If we encounter multilayer pore filling in your samples the regression will have been performed with out including the step although the data points are included in the plot and data set References Langmuir I 1916 The constitution and fundamental properties of solids and liquids Journal of the Alnerican Chemical Society 38 22212295 Mavor MJ Owm LB and Pratt TJ 1990 Measurement and evaluation of isotherm data Proceedings of 65th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers SPE 20728 157170